In membranes of cellulose acetates it is generally known (German Auslegeschrift No. 1,100,941) to improve wettability with the aid of the addition of commercial wetting agents.
Furthermore, it is known to carry out the drying of ultrafiltration membranes after impregnation with glycerin. The impregnation is intended to prevent an irreversible flow-through reduction and embrittlement or shrinkage. According to this method, a sufficient wettability of the dried cellulose triacetate membrane cannot be achieved, however, and the flow-through or passage output is below the original value prior to drying. If the membrane is to be employed as ultra- and hemofiltration membrane in the medical field, the use of wetting agents is precluded a priori.